1. Field of the Invention
The invention relates to an optical disc drive, more particularly to a method for detecting stable rotation speed of a spindle motor in an optical disk drive, and to an optical disc drive including a detection device for detecting stable rotation speed of a spindle motor in the optical disc drive.
2. Description of the Related Art
For reproduction and recording operations of an optical disc in an optical disc drive, stability of the rotation speed of the optical disc will affect whether the reproduction or recording operation can be processed smoothly by the optical disc drive. In other words, stability of the rotation speed of the spindle motor is essential to ensure good reproduction and writing results.
Referring to FIG. 1, a conventional optical disc drive is shown to have an optical disc 10 placed thereon, and includes a control unit 11 for controlling overall operations of the optical disc drive, a spindle motor (or disc motor) 12 for driving rotation of the optical disc 10, a motor driver 13 coupled to the control unit 11 and the spindle motor 12 for receiving control signals from the control unit 11 and for controlling operation of the spindle motor 12 in response to the control signals received thereby, and an optical pickup 14 coupled to the control unit 11 for reproducing data from or for writing data into the optical disc 10.
When driving the spindle motor 12 to rotate the optical disc 10, the control unit 11 generates a disc motor control output (DMO) that is received by the motor driver 13, which subsequently drives rotation of the spindle motor 12. As the spindle motor 12 rotates the optical disc 10, the control unit 11 can control the optical pickup 14 for reproducing data from or for writing data into the optical disc 10. Moreover, the spindle motor 12 includes a motor frequency pulse generator 121 for detecting rotation speed of the spindle motor 12 and for providing a frequency pulse generator signal (FG), which corresponds to the detected rotation speed, to the control unit 11, such that the control unit 11 can keep track of the rotation status of the spindle motor 12 and adjust the disc motor control output (DMO) accordingly.
There are many factors that can affect rotation speed of the spindle motor 12. For example, initial activation of the spindle motor 12, acceleration/deceleration during a burning process of the optical disc 10, writing after a track jump operation, etc., result in a transition period where the rotation speed of the spindle motor 12 is unstable. As shown in FIG. 2, when the disc motor control output (DMO) changes from an initial value (V1) to an adjusted value (V2), a transition period (T0) is required before the disc motor control output (DMO) stabilizes at the adjusted value (V2). If a reproduction or writing operation is performed within the transition period (T0), the quality of data reproduced from or written into the optical disc 10 will be poor. Moreover, in case of data writing, the writing position on the optical disc 10 may deviate and hinder subsequent data reproduction.
Therefore, in the conventional optical disc drive, data reproduction and writing generally proceed under the control of the control unit 11 only after an estimated transition period (T0) has elapsed. However, due to variations in characteristics of optical disc drives produced by different manufacturers, variations in characteristics of different optical discs, and variations in characteristics of an optical disc drive after a period of use, the duration of the requisite transition period (T0) may vary within a relatively large range. Thus, starting the reproduction or writing only after a preset transition period (T0) has elapsed may not be sufficient to ensure the stability of the rotation speed of the spindle motor 12 at the onset of the reproduction or writing operation. As such, the quality of data reproduced from or written into the optical disc 10 cannot be guaranteed.